(1) Field of the Invention
The present invention relates to a thermoplastic polyester resin composition, from which a molded article having excellent heat resistance and impact resistance can be obtained.
(2) Description of the Related Art
Thermoplastic polyesters, for example, polyalkylene terephthalates, have an excellent moldability, mechanical properties, heat-resistant stability, weatherability and electrically insulating properties, and therefore, are widely used as electrical and electronic parts, automobile parts and the like. Nevertheless, the application of these resins are considerably limited because the rigidity thereof at high temperature is low and the impact resistance thereof, especially the notched impact strength, is low.
The application of a thermoplastic polyester resin to a shell plate material of an automobile for on-line coating, utilizing its excellent mechanical and thermal properties has been attempted, but this application is not practically possible because the rigidity at high temperatures and the impact resistance are too low. If a glass fiber, carbon fiber, or wollastonite is filled in the thermoplastic polyester resin, the rigidity at high temperatures is improved, but the impact resistance and surface appearance become poor. If a rubber reinforcing resin is incorporated in the thermoplastic polyester resin, the impact resistance is improved, but the heat resistance represented by the modulus of elasticity at high temperatures becomes low and the resulting composition cannot withstand on-line coating. Moreover, since the linear expansion coefficient is large and sink marks are conspicuous on a rib or boss of a molded article, the composition cannot be applied to a shell plate of an automobile.
It is taught in Japanese Examined Patent Publication No. 51-21664 that the molding processability of a polyphenylene ether resin can be improved by incorporating polyethylene terephthalate or polybutylene terephthalate, but a satisfactory impact resistance cannot be obtained by this proposal.
The inventors previously proposed a composition comprising a polyester resin, a polycarbonate resin, a graft copolymer and a polyphenylene ether resin (Internation Publication No. 88-04310). In this composition, the heat resistance, impact resistance and linear expansion coefficient are improved, but the impact resistance is still low and the composition cannot be applied to an article for which a high impact resistance is required, for example, a fender and a bumper.